'\" t
.TH "SD_JOURNAL_OPEN" "3" "" "systemd 256.7" "sd_journal_open"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
sd_journal_open, sd_journal_open_directory, sd_journal_open_directory_fd, sd_journal_open_files, sd_journal_open_files_fd, sd_journal_open_namespace, sd_journal_close, sd_journal, SD_JOURNAL_LOCAL_ONLY, SD_JOURNAL_RUNTIME_ONLY, SD_JOURNAL_SYSTEM, SD_JOURNAL_CURRENT_USER, SD_JOURNAL_OS_ROOT, SD_JOURNAL_ALL_NAMESPACES, SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE, SD_JOURNAL_TAKE_DIRECTORY_FD \- Open the system journal for reading
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-journal\&.h>
.fi
.ft
.HP \w'int\ sd_journal_open('u
.BI "int sd_journal_open(sd_journal\ **" "ret" ", int\ " "flags" ");"
.HP \w'int\ sd_journal_open_namespace('u
.BI "int sd_journal_open_namespace(sd_journal\ **" "ret" ", const\ char\ *" "namespace" ", int\ " "flags" ");"
.HP \w'int\ sd_journal_open_directory('u
.BI "int sd_journal_open_directory(sd_journal\ **" "ret" ", const\ char\ *" "path" ", int\ " "flags" ");"
.HP \w'int\ sd_journal_open_directory_fd('u
.BI "int sd_journal_open_directory_fd(sd_journal\ **" "ret" ", int\ " "fd" ", int\ " "flags" ");"
.HP \w'int\ sd_journal_open_files('u
.BI "int sd_journal_open_files(sd_journal\ **" "ret" ", const\ char\ **" "paths" ", int\ " "flags" ");"
.HP \w'int\ sd_journal_open_files_fd('u
.BI "int sd_journal_open_files_fd(sd_journal\ **" "ret" ", int\ " "fds[]" ", unsigned\ " "n_fds" ", int\ " "flags" ");"
.HP \w'void\ sd_journal_close('u
.BI "void sd_journal_close(sd_journal\ *" "j" ");"
.SH "DESCRIPTION"
.PP
\fBsd_journal_open()\fR
opens the log journal for reading\&. It will find all journal files automatically and interleave them automatically when reading\&. As first argument it takes a pointer to a
\fIsd_journal\fR
pointer, which, on success, will contain a journal context object\&. The second argument is a flags field, which may consist of the following flags ORed together:
\fBSD_JOURNAL_LOCAL_ONLY\fR
makes sure only journal files generated on the local machine will be opened\&.
\fBSD_JOURNAL_RUNTIME_ONLY\fR
makes sure only volatile journal files will be opened, excluding those which are stored on persistent storage\&.
\fBSD_JOURNAL_SYSTEM\fR
will cause journal files of system services and the kernel (in opposition to user session processes) to be opened\&.
\fBSD_JOURNAL_CURRENT_USER\fR
will cause journal files of the current user to be opened\&. If neither
\fBSD_JOURNAL_SYSTEM\fR
nor
\fBSD_JOURNAL_CURRENT_USER\fR
are specified, all journal file types will be opened\&.
.PP
\fBsd_journal_open_namespace()\fR
is similar to
\fBsd_journal_open()\fR
but takes an additional
\fInamespace\fR
parameter that specifies which journal namespace to operate on\&. If specified as
\fBNULL\fR
the call is identical to
\fBsd_journal_open()\fR\&. If non\-\fBNULL\fR
only data from the namespace identified by the specified parameter is accessed\&. This call understands two additional flags: if
\fBSD_JOURNAL_ALL_NAMESPACES\fR
is specified the
\fInamespace\fR
parameter is ignored and all defined namespaces are accessed simultaneously; if
\fBSD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE\fR
the specified namespace and the default namespace are accessed but no others (this flag has no effect when
\fInamespace\fR
is passed as
\fBNULL\fR)\&. For details about journal namespaces see
\fBsystemd-journald.service\fR(8)\&.
.PP
\fBsd_journal_open_directory()\fR
is similar to
\fBsd_journal_open()\fR
but takes an absolute directory path as argument\&. All journal files in this directory will be opened and interleaved automatically\&. This call also takes a flags argument\&. The flags parameters accepted by this call are
\fBSD_JOURNAL_OS_ROOT\fR,
\fBSD_JOURNAL_SYSTEM\fR, and
\fBSD_JOURNAL_CURRENT_USER\fR\&. If
\fBSD_JOURNAL_OS_ROOT\fR
is specified, journal files are searched for below the usual
/var/log/journal
and
/run/log/journal
relative to the specified path, instead of directly beneath it\&. The other two flags limit which files are opened, the same as for
\fBsd_journal_open()\fR\&.
.PP
\fBsd_journal_open_directory_fd()\fR
is similar to
\fBsd_journal_open_directory()\fR, but takes a file descriptor referencing a directory in the file system instead of an absolute file system path\&. In addition to the flags accepted by
\fBsd_journal_open_directory()\fR, this function also accepts
\fBSD_JOURNAL_TAKE_DIRECTORY_FD\fR\&. If
\fBSD_JOURNAL_TAKE_DIRECTORY_FD\fR
is specified, the function will take the ownership of the specified file descriptor on success, and it will be closed by
\fBsd_journal_close()\fR, hence the caller of the function must not close the file descriptor\&. When the flag is not specified,
\fBsd_journal_close()\fR
will not close the file descriptor, so the caller should close it after
\fBsd_journal_close()\fR\&.
.PP
\fBsd_journal_open_files()\fR
is similar to
\fBsd_journal_open()\fR
but takes a
\fBNULL\fR\-terminated list of file paths to open\&. All files will be opened and interleaved automatically\&. This call also takes a flags argument, but it must be passed as 0 as no flags are currently understood for this call\&. Please note that in the case of a live journal, this function is only useful for debugging, because individual journal files can be rotated at any moment, and the opening of specific files is inherently racy\&.
.PP
\fBsd_journal_open_files_fd()\fR
is similar to
\fBsd_journal_open_files()\fR
but takes an array of open file descriptors that must reference journal files, instead of an array of file system paths\&. Pass the array of file descriptors as second argument, and the number of array entries in the third\&. The flags parameter must be passed as 0\&.
.PP
\fIsd_journal\fR
objects cannot be used in the child after a fork\&. Functions which take a journal object as an argument (\fBsd_journal_next()\fR
and others) will return
\fB\-ECHILD\fR
after a fork\&.
.PP
\fBsd_journal_close()\fR
will close the journal context allocated with
\fBsd_journal_open()\fR
or
\fBsd_journal_open_directory()\fR
and free its resources\&.
.PP
When opening the journal only journal files accessible to the calling user will be opened\&. If journal files are not accessible to the caller, this will be silently ignored\&.
.PP
See
\fBsd_journal_next\fR(3)
for an example of how to iterate through the journal after opening it with
\fBsd_journal_open()\fR\&.
.PP
A journal context object returned by
\fBsd_journal_open()\fR
references a specific journal entry as
\fIcurrent\fR
entry, similar to a file seek index in a classic file system file, but without absolute positions\&. It may be altered with
\fBsd_journal_next\fR(3)
and
\fBsd_journal_seek_head\fR(3)
and related calls\&. The current entry position may be exported in
\fIcursor\fR
strings, as accessible via
\fBsd_journal_get_cursor\fR(3)\&. Cursor strings may be used to globally identify a specific journal entry in a stable way and then later to seek to it (or if the specific entry is not available locally, to its closest entry in time)
\fBsd_journal_seek_cursor\fR(3)\&.
.PP
Notification of journal changes is available via
\fBsd_journal_get_fd()\fR
and related calls\&.
.SH "RETURN VALUE"
.PP
The
\fBsd_journal_open()\fR,
\fBsd_journal_open_directory()\fR, and
\fBsd_journal_open_files()\fR
calls return 0 on success or a negative errno\-style error code\&.
\fBsd_journal_close()\fR
returns nothing\&.
.SH "NOTES"
.PP
All functions listed here are thread\-agnostic and only a single specific thread may operate on a given object during its entire lifetime\&. It\*(Aqs safe to allocate multiple independent objects and use each from a specific thread in parallel\&. However, it\*(Aqs not safe to allocate such an object in one thread, and operate or free it from any other, even if locking is used to ensure these threads don\*(Aqt operate on it at the very same time\&.
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.SH "HISTORY"
.PP
\fBsd_journal_open()\fR,
\fBsd_journal_open_directory()\fR, and
\fBsd_journal_close()\fR
were added in version 187\&.
.PP
\fBsd_journal_open_files()\fR
was added in version 205\&.
.PP
\fBsd_journal_open_directory_fd()\fR
and
\fBsd_journal_open_files_fd()\fR
were added in version 230\&.
.PP
\fBsd_journal_open_namespace()\fR
was added in version 245\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-journal\fR(3), \fBsystemd-journald.service\fR(8), \fBsd_journal_next\fR(3), \fBsd_journal_get_data\fR(3)
